Unit switch-control system for electric motors.



E. LEHR. v UNIT SWITCH CONTROL SYSTEM FOR ELEGI'BIG MOTORS.

APPLmA nox Hum Jun: 8, 1907.

992,217. Patented May 16, 1911.

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UNIT swrrcrnconrnon SYSTEM non ELECTRIC Morons.

Specification of Letters Patent:

Application filed June 8, 1907; Serial 1705377324.

To all whom 'it may concern:

Be it known that I, Enwrs LEIIR, a citizen of the United States. and aresident of Wilkinsburg. in the county, of Allegheny and State ofPennsylrauia, have invented a new and. useful Improvement. in UnitSwitch-Control Systems for Electric Hotors,.of which the following is aspecifica- 'tion.

.My invention relates to systems of electrlc motor control and it hasfor its ob ect to provide a' system of this class comprising a pluralityof independently operated switches that are specially adapted forgoverning the secondary resistances of induction 1-mot ors.

In starting a relatlvely large lnduction inotor it-is desirable toconnect a suitable resistance in its secondary circuit. As the speed ofthe motor increases, this resistance may be gradually short-circuited,unless it is specially designed for regulating the mo- According to mypresent invention, I pro: ride a plurality of independently operated 3;\"ltCl1QS for controlling the secondary resistance of such a motor; aseries relay switch and intermediate relay switches be- -1ng providedfor delaying the closure of the control switches. I v

' .The single figure of the accompanying energy from a three-phasesource 5.

drawings, is a diagrammatic View of a control svstem arranged inaccordance with my invention.

Referring to the drawing, an induction motor 1 having a stationarymember 2, a rotatable member 3 and a secondary resistance 4, is suppliedwith alternating current Y The circuit connectionstor the'motor and itsresistance are controlled by switches 6, 7 8,9,

.-.1Q, and-11that :aregoverned by a series relay-switch.v -12 jandintermediate relay :=sw-itches' 13 and 14-. The control switches areelectrically operated and are supplied with-energy from.a.controlcircuitlolfi through a single point master switch 17.-

Although a three-phase motor is illustrat-ed and although the con'trolswitches are electrically operated, myinvention 1s, of

course,'not restricted in this regard and it is conceivable thatvarious-moditicat1ons may be eti'ected 1n the arrangement of the cirni}invention.

cuits without departing from the spirit of assuming that the switchesoccupy the positions shown In -the draw1ng;'1't the mas.-

plied from control line conductor 16 through the switch 1 7, anoperatingmagnet winding 18 of the switch 6 and conductor-19 to the oppositecontrol lineconductor 15.. When the coil 18 is energized, the switch 6is closed and energy is supplied to the motor from the generator 5through line conductorsQO,

21. and and the switch 6f The relay switch 12is provided with. an

Patented May 16, 1911 ter' switch 17 is closed energy will be.supoperating magnet winding 23 which is connected in series with linecircuit 22 and, consequently, the control circuit is openedwhen thecurrent traversing the motor circuit exceeds a predetermined amount. Themagnet winding 23 is preferably designed in such. a manner that theswitch is closed under ductor 25, contact members 26 (which, are

bridged by contact member 27 when the switch 6 is closed), conductor 28,contact members 29 (which are bridged by a contaet member 30 when theswitch 7 is open),

conductor 31'and the relay switch 12 to the line conductor 15. Relayswitch 13 may now be closed, provided switches-6 and 12 are closed andswitch 7 is open. i

The closure of the relayswitch 13' completes an operating magnet circuitfor clos ing the switch 7 as follows: from conductor 16, magnet winding32 of the switch 7 conductor 33, contact members '34: (which are bridgedby'a contactmember 35 when the switch 6 is closed), conductor 36,- relayswitchlS, conductor 37 and limit switch 12 to the opposite lineconductor 15.. The switch 7 is thus closed and aportion or theresistance 4 is short circuitedQsuch action being delayed-by the closureof the may switch 12 and the relay switch 13. As soon as the switch 7 isclosed, another circuit-is established from the operating magnet winding32 through conductor 38, contact members 39 (which are bridged bycontact member 40); and conductors 4'1 and 19, to the switch 12 to theline conductor 15.

conductor 15, so that switch 7- is held in this in thontotor circuit aresuch as to energize position, independently of the subsequent action ofthe limit or relay switches. Following the closure of the switch '7, acircuit is also established through an operating magnet winding 42 ofthe relay switch 1. L, conductor 43, contact members 44 (which arebridged by a contact member 1-5), conductor 2 -16, contact members 47(which are bridged by a contact member 48, when the switch 8 is open),conductors 31 and 37 and the The contact member 30 moves out ofengagement with the contact members 29, so that the relay switch 13 ispermitted to open at this point. The relay switch 14 is dependent uponthe switch 8 being'opened and the switch 12 being closed and it will beobserved that the switch 8 is closed after the closure of the s *itch14, a circuit being es tablished from the conductor 16 through operatingmagnet winding 4:9 of the switch 8, conductor 50, contact fingers 51(which are bridged by contact member 52, when the switch 7 is closed),conductor 53, switch 14:, conductor 37 and switch 12 to the lineconductor 15. In a similar manner. the switches 9 and 11 are dependentupon the closure of the relay switch 13, and the switches 8 and 10 aredependent upon the closure of the relay switch 14. By this means. theaction of the switches is delayed not only until the switch 12 is closedbut also until either one or the other of the switches 13 and 14 isclosed.

The proper sequence of operation for the switches 6 to 11.. inclusive.is insured by the interlocking of their circuits in conjunction withtheir intermediate relay switches 13 and 14-.

The switches T to 10. when closed, successively short-circuit a greaterportion of the resistance 4 and finally the switch 11 shortcircuits theentire resistance.

During the automatic acceleration of the motor, the control switches aresometimes closed in such rapid succession that the series relay switchdoes not have time to delay their closure. In such cases. it the closingcircuit of a control switch is once interrupted and the holding circuitclosed. the switch will remain in a closed position. but, if the seriesrelay acts after the switch has started to close and before its closingcircuit is interrupted an arc will be formed at the terminals of theseries relay switch which will be aiiplitied by the inductance in theswitch magnet windings.

One of the principal advantages of my invention lies in the fact thatthe intermediate relay switches 13 and 14 are so designed and connectedin cir uit that they automatically delay the closure of the successivecontrol switches until the series relay has had time to act, providedthe conditions the magnet winding 23 of the series relay.

Having thus described my invention, what I claim and desire to secure byLetters Patcut, is:

1. In a control system, the combination with an electric motor, a supplycircuittheretor, a resistance for the motor and a plurality ofindependently operated resistance-controlling switches, of a seriesrelay switch and a pair of intermediate relay switches that alternatelycooperate with the series relay switch to delay the action of theresistance-controlling switches.

2. In a control system, the combination with an electric motor, a supplycircuit therefor, a resistance for the motor and a plurality ofindependently operated resistance-controlling switches, of a limitingdevice, and intermediate relay switches for delaying the action of theresistance-controlling switches, each resistance-controlling switchbeing dependent upon the limiting device and one of the intermediaterelay switches. 0

3. In a'control system, the combination with an induction motor havingprimary and secondary members, a resistance for the secondary and aplurality of independently operated resistance-controlling switches, ofa limit switch and a pair of intermediate relays for delaying the actionof the resistance-controlling switches.

4. In a control system, the combination with an induction motor havingprimary and secondary members, a resistance for the secondary member. aplurality of independently operated resistance-controlling switches, andan independent control circuit, of a limit switch operated by the motorcurrent and relay switches governed by the limit switch and actingalternately to delay the action of the successive resistance-controllingswitches.

5. In a control system, the combination with a plurality of controlswitches adapted to close in a predetermined sequence, of a series-relayswitch and plurality of intermediate relay switches that alternatelydelay the action of the successive control switches to permit theseries-relay switch to act after ach control switch is closed.

6. In a control system. the combination with a. plurality of controlswitches adapted to close in a predetermined sequence, of a series-relayswitch and a pair of intermediate relay switches that alternately act incon junction with the series-relay switch to delay the closure of thesuccessive control switches.

7. In a control system, the combination with a plurality ofindependently operated 3 control switches adapted to close 1n apredetermined sequence, of a series relay switch and intermediate rela-yswitches which alternately delay the closure of the successlve controlswitches and insure normal operation :of the series-relay switch.

8. In a control system, the combination with an'induction motor havingprimary and secondary windings, a resistanoe for the secondary circuit,a plurality of independently operated resistance-controlling switcheshaving actuating magnetwindings, and an independent supply circuit forthe actuating magnets, of a series-relay switch,- and intermediate relayswitches cooperating In testimony whereof, I have hereunto subscribed myname this 31st day of May, 1907.

EDWIN LEHR.

\Yitnesses Ross W. COPELAND, BIRNEY HINES.

